/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 
 class Solution{
 public:
     TreeNode* invertTree(TreeNode* root){
         if(root == nullptr)
         {
            return nullptr;
         }
         TreeNode* left = invertTree(root->left);
         TreeNode* right = invertTree(root->right);
         root->left = right;
         root->right = left;
         return root;
     }
 };
